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By
Wikipedia,
The Boeing Model 247 was an early United States airliner, considered the first such aircraft to fully incorporate advances such as all-metal (anodized aluminum) semi-monocoque construction, a fully cantilevered wing, wing flaps and retractable landing gear. Other advanced features included control-surface trim tabs, an autopilot, and deicing boots for the wings and tailplane. The 247 first flew on February 8, 1933, and entered service later that year. Subsequently, development in airliner design saw engines and airframes becoming larger, and four-engine designs emerged, but no significant changes to this basic formula appeared until cabin pressurization and high-altitude flight were introduced in the early 1940s with the first pressurized airliner, the 307 Stratoliner. Design and development
Boeing had eclipsed other aviation manufacturers by introducing a host of aerodynamic and technical features into a commercial airliner. This advanced design which was a progression from earlier Monomail (Models 200, 221, 221A) and B-9 bomber designs, combined speed and safety. The Boeing 247 was faster than the U.S. premier fighter aircraft of its day, the Boeing P-12, which was an open-cockpit biplane. In addition, the 247 was the first twin-engine passenger transport able to fly on one engine. With controllable pitch propellers (standard equipment on the 247D), the 247 could maintain 11,500 ft at maximum gross takeoff weight. Its combination of features set the standard for the Douglas DC-1 and other airliners before World War II and was ordered "off the drawing board". Originally planned as a 14-passenger airliner powered by Pratt & Whitney R-1690 Hornet radial engines, the preliminary review of the design concept by United Airlines' pilots had resulted in a re-design to a smaller, less capable design configuration. Nonetheless, the 247 was a remarkable achievement and was the company's showcase exhibit at the 1933 Chicago World's Fair.
The cockpit windshield (windscreen) of the first 247s was angled forward instead of the conventional aft sweep. This was the Boeing solution to the problem of lighted control-panel instruments reflecting off the windshield at night, but it came at a significant performance penalty - this was one reason that the contemporary DC airliners could post comparable or superior performance while carrying significantly greater loads. By the introduction of the 247D, the pilot windshield was sloped aft at about the same angle as the DC-3's windows, and the night-glare problem was resolved by installing an extension {the glarescreen) over the control panel. The main landing gear did not fully retract; a portion of the wheels extended below the nacelles, typical of designs of the time, as a means of reducing structural damage in a wheels-up landing. The tailwheel was not retractable. While Boeing's 247 and 247A had speed-ring engine cowlings and fixed-pitch propellers, the Model 247D incorporated NACA cowlings and variable pitch propellers. Operational historyAs the 247 emerged from its test and development phase, the company further showcased its capabilities by entering a long-distance air race in 1934, the MacRobertson Race from England to Australia. During the 1930s, aircraft designs were often proven in air races and other aerial contests. A modified 247D was entered, flown by Col.Roscoe Turner and Clyde Pangborn.The 247, race number "57," was essentially a production model but all airliner furnishings were deleted to accommodate additional fuselage fuel tanks (eight in total). The MacRobertson Race attracted aircraft entries from all over the globe including prototypes as well as established production types with the grueling course considered an excellent proving ground as well as an opportunity to gain worldwide attention. Turner and Pangborn came in second place in the transport section (and third overall), behind the Boeing 247's eventual rival, the new Douglas DC-2. Winner of the 1934 US Collier Trophy for excellence in aviation design, the first 247 production orders were earmarked for Boeing Air Transport. The 247 was capable of crossing the United States from east to west eight hours faster than their predecessors, such as the Ford Trimotor and Curtiss Condor. Entering service on May 22, 1933, a Boeing Air Transport 247D set a cross-country record pace of 19½ hours on its San Francisco to New York inaugural flight. Due to the initial demand from U.S. air carriers, Boeing sold the first 60 247s, an unprecedented $3.5 million order to its affiliated airline, Boeing Air Transport (part of the United Aircraft and Transport Corporation, UATC), at a unit price of $65,000. TWA (Transcontinental & Western Air) also ordered the 247 but UATC declined the order, which resulted in TWA President Jack Frye setting out the requirements for a new airliner and funding Don Douglas to design and build the Douglas DC-1 prototype. Douglas eventually developed the design into the historic and enormously successful DC-3 line. Although the Boeing design had been the first to enter series production, the 247 proved to have some serious design deficiencies. Air carriers considered its limited capacity a drawback since it only carried ten passengers, in five rows with a seat on each side of the aisle, as well as a flight attendant. Compared to the more capacious DC-2 and later DC-3, the passenger count was too few to make it a commercially viable airliner. Another feature influencing passenger comfort was, the 247's main wing spar ran through the cabin area, so persons moving through the cabin had to make a large step over it. The Lockheed L-10 Electra had a similar configuration and while it was a more compact design, the Electra managed to carry the same number of passengers at a slightly better overall performance, and more importantly, at a lower cost-per-mile. Seventy-five 247s were built; by contrast, Douglas produced over 10,000 DC-3s, including wartime production of C-47, while the rival Lockheed Electra "family" was eventually to reach over 3,000 in its various civilian and military variants. Boeing Air Transport bought 60 examples, United Aircraft Corp. (10), four went to Lufthansa, and one a private owner in China. While the industry primarily standardized on Boeing's competitors, many of United's aircraft were later purchased by Western Air Express at "bargain basement prices".
The 247 remained in airline service until World War II, when several were converted into C-73 transports and trainers. No. 121 Squadron Royal Canadian Air Force (RCAF) operated seven Model 247Ds as medium transports during the early part of the war. Some 247s were still flying in the late 1960s, converted either into cargo transports or personal business aircraft. A number of specially modified variants included a Boeing 247Y appropriated from United for Air Corps use as a test aircraft fitted with two machine guns in the nose. The same installation later was fitted to a 247Y owned by Generalissimo Chiang Kai-Shek; this aircraft also featured a Colt .50 caliber machine gun in a flexible mount. A 247D purchased by the British Royal Air Force became a test mule for new equipment, featuring a nonstandard nose, new powerplants and non-retracting gear. The Turner/Pangborn 247D still exists. Originally flown on September 5, 1934, it was leased from United Airlines for the 1934 MacRobertson Race and returned to United where it served in regular airline service until 1937. Subsequently, the 247D was sold to the Union Electric Company of St. Louis for use as an executive transport. The Air Safety Board purchased the aircraft in 1939 and it remained in use for 14 years before it was donated to the National Air and Space Museum, Washington, DC. Displayed today with two sets of markings, the left side is marked as NR257Y, in Colonel Turner's 1934 MacRobertson Race colors, while the right side is painted in United Airlines livery, as NC13369. Incidents and accidentsOn October 10, 1933, a United Airlines 247 was the victim of the first proven case of sabotage of a commercial airliner. The aircraft, en route from Cleveland to Chicago, was destroyed by a nitroglycerin-based explosive device over Chesterton, Indiana. On January 12, 1937, a Western Air Express 247 flight from Salt Lake City to Burbank crashed near Newhall, California, killing Martin Johnson of Martin and Osa Johnson fame (photographers, explorers, marketers, naturalists and authors). Operators
Civil operators
Military operatorsSurvivors
Specifications (Boeing 247D)Data from The Concise Guide to American Aircraft of World War II General characteristics
Performance
See alsoRelated development Comparable aircraft
External links
Text from Wikipedia is available under the Creative Commons Attribution/Share-Alike License; additional terms may apply.
Published in July 2009. Click here to read more articles related to aviation and space!
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